The development of synthetic methodologies for the introduction of sulfurpentafluoride or pentafluorosulfuranyl groups (“SF5”) into organic compounds has been pursued with a considerable degree of interest. The SF5 group imparts unique properties to these organic compounds that include, inter alia, low surface energy, high chemical resistance, high thermal stability, high electronegativity, hydrophobicity, and high dielectric constant. The high electronegativity value of the SF5 group, 3.62 on the Pauling scale, and its greater electron withdrawing ability makes it an attractive alternative for the trifluoromethyl group (“CF3”) found in many commercial products. Illustrative of such compositions containing SF5 include pentafluorosulfuranyl fluoroaliphatic compositions, sulfur pentafluorophenyl pyrazoles, and arylsulfur pentafluorides, the latter finding applications in liquid crystals.
The following articles and patents are representative of methods for introducing SF5 groups into organic compounds.
U.S. Pat. No. 4,535,011 discloses a process for producing mono(pentafluorosulfur diacetylene polymers wherein sulfur pentafluoro bromide is first reacted with acetylene at temperatures below about −70° C. and then the resulting intermediate debrominated. Dehydrobromination is effected by reacting the intermediate adduct with a strong base, e.g., potassium hydroxide.
U.S. Pat. No. 6,479,645 discloses methods for producing sulfurpentafluoride compounds having a substituted silyl group. In the disclosed process, sulfur pentafluoro bromide is reacted with a trisubstituted silyl acetylene in the presence of potassium fluoride at room temperature. Bromine is removed from the intermediate compound by addition of powdered potassium hydroxide.
The article, New and Convenient Method for Incorporation of Pentafluorosulfanyl (SF5) Substituents Into Aliphatic Organic Compounds, Samai Ayt-Mohand and W. Dolbier, Organic Letters, 2002, 4, 17, 3013 discloses the addition of the SF5-group to organic compounds by the reaction of SF5Cl with alkynes and alkenes in the presence of triethylborane and hexane solvent at temperatures from −30° C. to room temperature.
Sheppard, et al, W. A. J. Am. Chem. Soc. 1962, 84, 3064., disclose the formation of phenylsulfur pentafluoride and nitrophenylsulfur pentafluoride by reacting aryl disulfides with silver difluoride in ˜30% yield.
Bowden, R. D., et al, D. Tetrahedron, 2000, 56, 3399, disclose the reaction of aryl disulfides with F2 in the presence of CH3CN. This reaction produces electron-deficient arylsulfur pentafluorides, e.g., ortho and para nitrophenylsulfur pentafluoride.
Hoover, F. W; et al., J. Am. Chem. Soc. 1964, 3567, disclose a procedure for the production of phenylsulfur pentafluoride and dimethylphenylsulfur pentafluoride by the Diels-Alder cycloaddition reaction of butadiene and 2,3-dimethylbutadiene respectively with ethynylsulfur pentafluoride.